NASA’s 2026 comparison of Pacific Ocean color shows a green-hued area shrinking as a bluer shade spreads across part of the western equatorial Pacific. The map represents apparent visible wavelength, a color measure calculated from ocean observations by the Ocean Color Instrument aboard NASA’s PACE satellite. NASA associates the bluer signal with fewer phytoplankton in the affected area.
What NASA’s Pacific map measures
PACE’s Ocean Color Instrument measures hundreds of wavelengths of visible, near-infrared and ultraviolet light. NASA uses those observations to calculate an average ocean color called apparent visible wavelength. The 2026 comparison with 2025 shows the green-hued region shrinking in the western equatorial Pacific as bluer shades expand.
That color measure is an indicator of ocean conditions, not a count of every organism in the water. NASA links the signal to phytoplankton abundance, but the map does not inventory marine animals.
How El Niño can change the color signal
NASA connects the color shift to a sequence involving trade winds and nutrients. During El Niño, weaker trade winds reduce the upwelling of cold, nutrient-rich water from deeper in the ocean. With fewer nutrients reaching the surface, phytoplankton abundance falls in affected areas, and the ocean-color signal can become bluer.
Color, temperature and sea height are different measurements
NASA also reports eastern Pacific sea-surface temperatures about 3°F above the long-term average. That temperature anomaly is a separate measurement from PACE’s ocean-color signal.
Sea-surface height is measured separately, using satellite altimetry from the Sentinel-6 mission. NASA says the satellites measure ocean height every 10 days. Those height maps track a different property of the ocean and do not represent phytoplankton abundance.
What NOAA’s 83% forecast means
In its October 8, 2026 discussion, NOAA assigned an 83% probability to the three-month Relative Oceanic Niño Index (RONI) reaching +2.5°C or higher for October through December 2026. NOAA uses that threshold to define a historic-strength event exceeding El Niño events dating back to 1950.
NOAA made a separate forecast for January through March 2027: strong-to-very-strong El Niño conditions were likely, with the probability above 83%. The forecast makes El Niño-related impacts more likely, but it does not guarantee particular effects in every region.
